Db::key_range |
#include <db_cxx.h>int Db::key_range(DbTxn *txnid Dbt *key, DB_KEY_RANGE *key_range, u_int32_t flags);
The Db::key_range method returns an estimate of the proportion of keys that are less than, equal to, and greater than the specified key. The underlying database must be of type Btree.
The Db::key_range method fills in a structure of type DB_KEY_RANGE. The following data fields are available from the DB_KEY_RANGE structure:
Values are in the range of 0 to 1; for example, if the field less is 0.05, 5% of the keys in the database are less than the key parameter. The value for equal will be zero if there is no matching key, and will be non-zero otherwise.
The Db::key_range method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success.
The Db::key_range method may fail and throw DbException, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:
If a transactional database environment operation was selected to resolve a deadlock, the Db::key_range method will fail and either return DB_LOCK_DEADLOCK or throw a DbDeadlockException exception.
If a Berkeley DB Concurrent Data Store database environment configured for lock timeouts was unable to grant a lock in the allowed time, the Db::key_range method will fail and either return DB_LOCK_NOTGRANTED or throw a DbLockNotGrantedException exception.
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